Conventional three dimensional rendering includes monographic and stereo graphic rendering. Monographic rendering produces a three-dimensional projection onto a two-dimensional display. Typically monographic rendering utilizes depth testing, shading, and the like to project a three-dimensional scene on a display. Currently, monographic rendering is popularly utilized in computer games.
Stereographic rendering produces a left eye and right eye two-dimensional projection of three-dimensional data, in addition to depth testing, shading and the like, to produce an image that appears to have depth in front of and behind a display device when used, for example, in combination with shutter glasses. Two images may be generated by shifting a mono view along the x axis. In one implementation, each scene is copied and shifted by a parallax value to generate a left and right eye view 110, 120 of the scene, as illustrated in FIG. 1. The left and right eye views 110, 120 are then presented on a display 140 independently to each eye of the user. In one implementation, a pair of shutter glasses 120 are used in combination with a liquid crystal display (LCD), digital light processing (DLP) display or 3D projection unit 140 to present the stereoscopic scene. The left and right eye views 110, 120 are alternatively presented on the display 140 and the left and right lens of the shutter glasses 130 synchronously turn on and off to independently present the left and right eye views 110, 120 to each respective eye of the user to create the illusion of a three dimensional image. The resulting image appears to the user to have depth in front of and behind the stereoscopic three-dimensional display.
In a number of graphical rendering applications, a selection marquee may be used to indicate a selected area in the rendered image. For example, a user may use a pointing device to draw a box for selecting a region in the image. In monographic rendering, the selection marquee is naturally defined in the view space as a two-dimensional shape (e.g., rectangle, disc, free form shape). Therefore, the selection marquee can be simply drawn as the desired shape in the window space. However, in stereographic rendering the same solution does not work. Each view defines its own selection marquee volume in its clipping space. The vertical edges of the shape don't match in the right and left images. Accordingly, there is a need for an improved technique for displaying a selection marquee in stereographic rendering.